SLVM Single-Node Online Reconfiguration (SLVM SNOR)

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SLVM Online Volume Re-configuration

Abstract........................................................................................................................................2

Overview......................................................................................................................................2

Commands....................................................................................................................................4

vgchange(1M)............................................................................................................................4

Changing the mode to exclusive from shared ..............................................................................4

Changing the mode to shared from exclusive ..............................................................................4

Procedures ....................................................................................................................................5

Making a configuration change in an active shared volume group ......................................................5

Determining whether SLVM SNOR is available on the system.................................................................8

SLVM SNOR Messages ...................................................................................................................9

vgchange(1M)............................................................................................................................9

Required software and patch list......................................................................................................11

Summary of content (11 pages)

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SLVM Online Volume Re-configuration Abstract ........................................................................................................................................ 2 Overview ...................................................................................................................................... 2 Commands.................................................................................................................................... 4 vgchange(1M)..........................
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Abstract The SLVM Single Node Online volume Re-configuration (SNOR) feature allows changing the configuration of an active shared volume group in a cluster. SLVM (Shared Logical Volume Manager) is a mechanism that permits multiple systems in a ServiceGuard cluster to share (read/write) disk resources in the form of volume groups.
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With the SNOR functionality installed, to change the VG configuration, it is required that: 1. Applications using the VG are scaled down to one node. These applications are still running on that one node 2. The VG is deactivated on all but one node of the cluster. 3. The activation mode of the VG is changed to exclusive in a single node. 4. Change the configuration on the VG. 5.
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Commands vgchange(1M) A new option (-x) was added to the vgchange command to change the activation mode of a shared volume group. Changing the mode to exclusive from shared vgchange -a e -x vg_name The vgchange command provides a new "-x" option that must be used together with the existing "-a e" option to change the activation mode of a shared VG to exclusive mode. Upon success, the VG will be in the same state than if it had been activated in exclusive mode from inactive.
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Procedures Making a configuration change in an active shared volume group 1. Identify the shared volume group on which a configuration change is required. Call it vg_shared. 2. Identify one node of the cluster which is running an application (say SGeRAC) using the shared volume group. Call it node1. The applications using the volume group, vg_shared, on this node will remain unaffected during the procedure. The cluster application, SGeRAC, needs to be scaled down to the single cluster node node1. 3.
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. Export the changes to other cluster nodes if required. If the configuration change required the creation or deletion of a new logical or physical volume (i.e. any of the following commands were used: lvcreate(1M), lvreduce(1M), vgextend(1M), vgreduce(1M), lvsplit(1M), lvmerge(1M)), then the following sequence of steps is required.
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On node1, change the mode back to shared vgchange -a s -x vg_shared On the other cluster nodes, activate vg_shared in shared mode vgchange -a s vg_shared 8. As a last step, we recommend using vgcfgbackup on all nodes to backup the changes made to the volume group.
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Determining whether SLVM SNOR is available on the system SLVM SNOR is available in patch form for HP-UX 11i v1 and v2 and as standard in future HP-UX releases. Patches for LVM commands and kernel components, and the supported ServiceGuard version need to be installed on the system to enable the feature. It will not be available if patches for any of the three components are missing on the system.
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SLVM SNOR Messages vgchange(1M) 1. Usage: vgchange {-a Availability -q Quorum [-l] [-p] [-s] [VolumeGroupName... ]} {[-S shareable] -c cluster VolumeGroupName} {[-P parallel_nomwc_resync_count]} "x": Illegal option. This error is reported when the "-x" option to vgchange is used on a system that does not have the SNOR LVM Commands patch. Install the appropriate LVM command patch (see the Required software and patch list). 2.
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7. To change activation mode, use lvchange(1M) to disable the Mirror Write Cache flag for all Logical Volumes in "vg_shared". This error is reported when the "-x" option to vgchange is used, with mirrored logical volumes which have mirror consistency enabled but do not have the Mirror Write Cache flag off, and the requested activation mode is shared (refer lvchange(1M)). The Mirror Write Cache is never used when a volume group is activated shared. 8.
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Required software and patch list o For HP-UX 11i Version 1: LVM Patches PHKL_33390 and PHCO_33310 (or superseding patches) ServiceGuard patch PHSS_33834 on SG11.16. o For HP-UX 11i Version 2: LVM Patches PHKL_33312 and PHCO_33309 (or superseding patches) SG 11.17 release or ServiceGuard patch PHSS_33835 on SG11.16. © 2006 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.